protected override Expression VisitConstant(ConstantExpression node)
{
if (_addMode == true)
{
if ((node.Type.IsGeneric(typeof(EntityQueryable <>)) || node.Type.IsGeneric(typeof(EnumerableQuery <>))) && node.Type.GenericTypeArguments[0] == _modelType)
{
ParameterExpression pe = Expression.Parameter(_modelType);
ChangePara cp = new ChangePara();
//传递过来的where条件，其源类型不一定和表达式中原有的相符，所以先将新where条件的源类型修改成和query一样的
//也就是说新的where条件可能是 x=>x.id==1， 而在表达式中不一定有x，所以要先统一
var modifiedWhere = cp.Change(_where.Body, pe);
var rv = Expression.Call(
typeof(Queryable),
"Where",
new Type[] { _modelType },
node,
Expression.Lambda(modifiedWhere, new ParameterExpression[] { pe }));
return(rv);
}
}
return(base.VisitConstant(node));
}
/// <summary>
/// 检查方法调用类型的表达式
/// </summary>
/// <param name="node">表达式节点</param>
/// <returns>修改后的表达式</returns>
protected override Expression VisitMethodCall(MethodCallExpression node)
{
//如果不是添加模式，那么删除所有的order
if (_addMode == false)
{
var aType = node.Arguments[0].Type;
//如果节点是order
if (node != null && (node.Method.Name.ToLower() == "orderby" || node.Method.Name.ToLower() == "orderbydescending") && aType.GetTypeInfo().IsGenericType)
{
//继续往上找到不是where的节点
return(GetParentExpNotOrder(node));
}
}
//如果是添加模式
else
{
var modelType = node.Type.GenericTypeArguments[0];
List <SortInfo> info = new List <SortInfo>();
var temp = APIHelper.JsonDeserialize <List <SortInfo> >(_sortinfo);
info.AddRange(temp);
Expression rv = null;
foreach (var item in info)
{
ParameterExpression pe = Expression.Parameter(modelType);
Expression pro = Expression.PropertyOrField(pe, item.Property);
Type proType = modelType.GetProperty(item.Property).PropertyType;
ChangePara cp = new ChangePara();
cp.Change(pro, pe);
if (item.Direction == SortDir.Asc)
{
if (rv == null)
{
rv = Expression.Call(
typeof(Queryable),
"OrderBy",
new Type[] { modelType, proType },
node,
Expression.Lambda(pro, new ParameterExpression[] { pe }));
}
else
{
rv = Expression.Call(
typeof(Queryable),
"ThenBy",
new Type[] { modelType, proType },
rv,
Expression.Lambda(pro, new ParameterExpression[] { pe }));
}
}
if (item.Direction == SortDir.Desc)
{
if (rv == null)
{
rv = Expression.Call(
typeof(Queryable),
"OrderByDescending",
new Type[] { modelType, proType },
node,
Expression.Lambda(pro, new ParameterExpression[] { pe }));
}
else
{
rv = Expression.Call(
typeof(Queryable),
"ThenByDescending",
new Type[] { modelType, proType },
rv,
Expression.Lambda(pro, new ParameterExpression[] { pe }));
}
}
}
return(rv);
}
return(base.VisitMethodCall(node));
}